Scanning impedance microscopy of electroactive interfaces

A scanning probe technique based on the detection of the phase change of ca ntilever oscillations induced by a lateral bias applied to the sample is de veloped. This technique is used to investigate Sigma5 grain boundary in Nb- doped SrTiO3 bicrystal. Tip bias, frequency, and driving amplitude dependen ce of cantilever response to sample ac bias were found to be in excellent a greement with the theoretical model. This technique, further referred to as scanning impedance microscopy, allows mapping of the local phase angle of complex microstructures. This technique is complemented by scanning surface potential microscopy (SSPM). Ramping the lateral dc bias during SSPM measu rements allows the voltage characteristics of the grain boundary to be reco nstructed and dc transport properties to be obtained by an equivalent circu it method. The combination of scanning impedance microscopy and scanning su rface potential microscopy allows independent quantification of interface r esistivity and capacitance, thus providing spatially resolved impedance spe ctra of complex microstructures. (C) 2001 American Institute of Physics.